/* Copyright 2004, 2005, 2006 Acegi Technology Pty Limited
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.nw.web.utils;

import org.springframework.dao.DataAccessException;

/**
 * <p>
 * Interface for performing authentication operations on a password.
 * </p>
 * 
 * @author colin sampaleanu
 */
public interface PasswordEncoder {
	// ~ Methods
	// ========================================================================================================

	/**
	 * <p>
	 * Encodes the specified raw password with an implementation specific
	 * algorithm.
	 * </p>
	 * <P>
	 * This will generally be a one-way message digest such as MD5 or SHA, but
	 * may also be a plaintext variant which does no encoding at all, but rather
	 * returns the same password it was fed. The latter is useful to plug in
	 * when the original password must be stored as-is.
	 * </p>
	 * <p>
	 * The specified salt will potentially be used by the implementation to
	 * "salt" the initial value before encoding. A salt is usually a
	 * user-specific value which is added to the password before the digest is
	 * computed. This means that computation of digests for common dictionary
	 * words will be different than those in the backend store, because the
	 * dictionary word digests will not reflect the addition of the salt. If a
	 * per-user salt is used (rather than a system-wide salt), it also means
	 * users with the same password will have different digest encoded passwords
	 * in the backend store.
	 * </p>
	 * <P>
	 * If a salt value is provided, the same salt value must be use when calling
	 * the {@link #isPasswordValid(String, String, Object)} method. Note that a
	 * specific implementation may choose to ignore the salt value (via
	 * <code>null</code>), or provide its own.
	 * </p>
	 * 
	 * @param rawPass
	 *            the password to encode
	 * @param salt
	 *            optionally used by the implementation to "salt" the raw
	 *            password before encoding. A <code>null</code> value is legal.
	 * 
	 * @return encoded password
	 * 
	 * @throws DataAccessException
	 *             DOCUMENT ME!
	 */
	String encodePassword(String rawPass, Object salt) throws DataAccessException;

	/**
	 * <p>
	 * Validates a specified "raw" password against an encoded password.
	 * </p>
	 * <P>
	 * The encoded password should have previously been generated by
	 * {@link #encodePassword(String, Object)}. This method will encode the
	 * <code>rawPass</code> (using the optional <code>salt</code>), and then
	 * compared it with the presented <code>encPass</code>.
	 * </p>
	 * <p>
	 * For a discussion of salts, please refer to
	 * {@link #encodePassword(String, Object)}.
	 * </p>
	 * 
	 * @param encPass
	 *            a pre-encoded password
	 * @param rawPass
	 *            a raw password to encode and compare against the pre-encoded
	 *            password
	 * @param salt
	 *            optionally used by the implementation to "salt" the raw
	 *            password before encoding. A <code>null</code> value is legal.
	 * 
	 * @return true if the password is valid , false otherwise
	 * 
	 * @throws DataAccessException
	 *             DOCUMENT ME!
	 */
	boolean isPasswordValid(String encPass, String rawPass, Object salt) throws DataAccessException;
}
